Distinguishing the Roles of Thylakoid Respiratory Terminal Oxidases in the Cyanobacterium Synechocystis sp PCC 6803
Distinguishing the Roles of Thylakoid Respiratory Terminal Oxidases in the Cyanobacterium Synechocystis sp PCC 6803
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DOI：
10.1104/pp.16.00479
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发表时间：
2016-06-01
期刊：
影响因子：
7.4
通讯作者：
Allahverdiyeva, Yagut
中科院分区：
文献类型：
--
作者：
Ermakova, Maria;Huokko, Tuomas;Allahverdiyeva, Yagut
集胞藻6803的光合电子传递链中存在多种利用氧的电子汇，包括可溶性黄二铁蛋白（Flv 1/3）、细胞色素c氧化酶（考克斯）和细胞色素bd醌醇氧化酶（Cyd）等膜定位呼吸末端氧化酶（RTOs）。然而，与其他电子汇相比，单个RTO的作用及其相对重要性知之甚少，特别是在光照下。通过膜入口质谱气体交换，叶绿素a荧光，P700分析，和抑制剂治疗的野生型和各种突变体缺陷的RTO，Flv 1/3，和光系统I，我们研究了这些复合物的贡献，以缓解过剩的电子在光合链。据我们所知，我们第一次证明了Cyd在光下的氧摄取活性，尽管它仅在波动的光条件下抑制细胞色素B（6）f位点和Delta flv 1/3的电子转移后才被检测到，其中线性电子转移由于受损的光系统I活性而被急剧抑制。考克斯主要负责暗呼吸，并在强光下与P700竞争电子。只有Delta考克斯/cyd双突变体，而不是单突变体，表现出高度减少的质体醌池在黑暗中和受损的总氧释放在光下，表明类囊体为基础的RTO能够部分补偿对方。因此，这两个电子汇有助于缓解照明下的过量电子：RTO继续在光下发挥作用，在较慢的时间范围内和有限的规模上运行，而Flv 1/3作为光诱导成分迅速响应，具有更大的容量。
Various oxygen-utilizing electron sinks, including the soluble flavodiiron proteins (Flv1/3), and the membrane-localized respiratory terminal oxidases (RTOs), cytochrome c oxidase (Cox) and cytochrome bd quinol oxidase (Cyd), are present in the photosynthetic electron transfer chain of Synechocystis sp. PCC 6803. However, the role of individual RTOs and their relative importance compared with other electron sinks are poorly understood, particularly under light. Via membrane inlet mass spectrometry gas exchange, chlorophyll a fluorescence, P700 analysis, and inhibitor treatment of the wild type and various mutants deficient in RTOs, Flv1/3, and photosystem I, we investigated the contribution of these complexes to the alleviation of excess electrons in the photosynthetic chain. To our knowledge, for the first time, we demonstrated the activity of Cyd in oxygen uptake under light, although it was detected only upon inhibition of electron transfer at the cytochrome b(6)f site and Delta flv1/3 under fluctuating light conditions, where linear electron transfer was drastically inhibited due to impaired photosystem I activity. Cox is mostly responsible for dark respiration and competes with P700 for electrons under high light. Only the Delta cox/cyd double mutant, but not single mutants, demonstrated a highly reduced plastoquinone pool in darkness and impaired gross oxygen evolution under light, indicating that thylakoid-based RTOs are able to compensate partially for each other. Thus, both electron sinks contribute to the alleviation of excess electrons under illumination: RTOs continue to function under light, operating on slower time ranges and on a limited scale, whereas Flv1/3 responds rapidly as a light-induced component and has greater capacity.